Description: A grisly murder investigation leads Castle and Beckett to a suspect who claims he's traveled back in time to stop terrible events from unfolding, events that will change the course of human history. Is he simply a deluded killer, or is it possible that he's telling the truth. An agent of a future neo-fascist global government is sent back to kill a researcher, preventing him from developing force field technology that will allow his government to be overthrown. He brings back a copy of a coffee-stained note with information about the researcher on it. During the course of the episode, Castle and Beckett find the original note, and with the aid of another time traveler, apprehend the agent and save the researcher. At the end of the episode, Beckett spills coffee on the original note, establishing a predestination paradox.